Q.Why Won’t My Knockout Roses Bloom??
We planted 6 knock out roses in April of 2010. They bloomed during the 2010 season, but not what I expected. They have bloomed one time early in 2011 and have not bloomed since. We were told to plant them and water them, but that they did not need anything else. I have started feeding them with Miracle gro in the last week . . . I thought that would be better than nothing. Four of the plants have good foilage, but something stripped the leaves from 2 of the plants several weeks ago. I live in east Texas. Thanks for your input.
this may help as well:
https://www.gardeningknowhow.com/ornamental/flowers/knockout-roses/care-knockout-roses.htm
https://aggie-horticulture.tamu.edu/galveston/recovery/Testing-Your-Soil.pdf
This is a good link for you. I think whoever told you to just "plant them" might have misled you. Organic materials mixed in to our natives soils are necessary for best results. They need deep watering, not just a hit with a hose.